Ignition circuit



June 4, 1940. D. w. RANDOLPH,

IGNITION CIRCUIT Filed March 11, 1939 Zhwentdr flaw/d 24' 94.102

' Patented June ,'4,

IGNITION cutourr Donald w. Randolph, Flint, Mlcli.,.assignor to General Motors Corporation, Detroit, Mich, a I corporation of Delaware Application March 11, 1939, Serial No. 261,228

6 Claims.-

more specifically to an ignition system for providing igniton means for an internal combustion engine.

5 Since it is of course necessary to'provide some,

means for igniting the fuel in an internalcombustion engine and it has been conventional to provide such means by causing a high tension electric spark to jump across a set of terminals 10 provided within a cylinder to ignite said gas, it g has been a problemto supply such high tension current within .the cylinder in some manner so that the movable contacts or other contacting means utilized will not be burned or disintegrated 15 through long continued wear at a high rate. Utilizing mechanical breakers in such a system is not satisfactory since the are drawn between the two points of such a breaker cause disintegration of the contact surfaces and therefore 20 rapid wear and requires frequency replacement. It is therefore the object of my invention to provide means for making and breaking the circult through means wherein there is no mechanical movement orv disintegration of contact as members such as through tubes where current is allowed to flow or its flow prevented through potential diil'erences in the electrodes.

With the above and other objects in view, the embodiments of my invention will be best shown by reference to the following specification and claims and the illustrationsin the accompanying drawing, in which: Figure 1 is a schematic wiring diagram o'f an ignition system embodying my invention. 35 1 Figure 2 shows also-a'schematic wiring diagram of a modified form of a circuit embodying my invention.

Referring now speciflcallyto the showing of Figure 1, there is provided a suitable source of 0 power 2, an automatic circuit interrupter l, a

transformer 6, a resistance element 8, a condenser I ii, an electron tube l2 of the type commercially known as the Thyratron," 'an inductance coil It, a distributor l6 and a plurality of spark plugs IS. The mercury interrupter shown broadly at 4 consists of an. envelope 20 within which is supported a pool of mercury 22 havingimmersed therein a plurality of contacts 24, 26, the latter being a carbon electrode; only 50 a small portion 28 of which contacts the mercury path, the current flowing from this portion to the electrode 24. The localized heat adjacent .the surface-28 causes vaporation of the mercury and momentary circuit breakage which is imu mediately remade through condensation and thus (01. 123-148) This invention relatesv to ignition means and a periodic, automatic 21mm making and break ing. The electron tube I2 is provided with a series of electrodes such as input electrode ll,

a grid or control electrode 22 and a plate 24,

the latter being connected to the primary of the 5 inductance coil it through line 38 and the input electrode. being connected to the secondary of the transformer 8 through resistance 8. The grid is connected through a mechanical circuit breaker such as to the negative side of the battery 10 through line 40, the mechanical breaker 32 being i operated by the cam shaft of the motor to accurately time the opening and closing of the switch 28.

The operation of the system is as follows: The current from the battery 2 which is supplied to the primary of the transformer 6 is automatically, periodically interrupted so that the current may be transformed in any desired ratio from the primary to the secondary of the transformer. The current flowing in the. secondary through the supply from the primary is utilized to charge the condenser I. which is directly connected across the secondary. The potential across the .condenser I0 is therefore built up and this potentlal is present upon the input electrode" of the Thyratron tube. This potential after it has reached a certain degree would tend to flow to the plate 34 but this flow is prevented by a: negative biasing potential present on the grid 32, this negative potential being' applied through the closed, switch 38 and the line II from the battery;

However when the switch 38 is mechanically opened the negative bias on the grid 32 is reduced tential of the grid 32 has been'made less negative through the opening of the switch 38. It will thus be seen that the only mechanical switch utilized in the circuit is switch 38 and this switch only handles a very small negative current to the control grid so that its life will be practically indefinite, and the Thyratron tube having no moving parts or no arcingcontacts would have an indefinite life as well as the mercury .interrupter 4 so that I have provided a very simple and substantially long-lived system. as

current as applied in the, first instance which in-- creases to some extent theefliciency of the system and reduces the load on the battery; otherwise the operation is exactly the same as in the first instance.

I claim:

1. In an ignition system, a battery, interrupter means, a transformer primary connected in series with the battery and interrupter, a transformer secondary, a condenser charged from the secondary, a coil connected to and adapted 'to be supplied with current from the condenser and an electronic tube interposed between the condenser and coil having a control electrode and means for periodically varying the voltage on the control electrode to cause current to flow through the tube at given intervals. f

2. In an ignition system, a source of alternating current, means for rectifying the same, condenser means supplied from the rectifier, electronic valve means connected to the condenser output, and an induction coil also connected to the condenser and the valve whereby the latter controls the energization of the coil from the alternating source.

3 In an ignition system, a source of alternating current, means for rectifying the same, condenser means supplied from the rectifier, electronic valve means connected to the condenser output, an induction 0011 also connected to the condenser and the valve whereby the latter controls the energization of the coil from the alternating source, and periodic timing means controlling valve operation whereby the coil energization is entirely separate from the frequency of the alternating source. l

4. In an ignition system, a direct current source of power, an automatic mercury interrupter connected thereto, a condenser connected to the interrupter output, an induction coil fed by the condenser and an electronic valve between the condenser and the coil to control flow therebetween.

5. In an ignition system, a direct current source of power, an automatic mercury interrupter connected thereto a condenser connected to the interrupter output, an induction coil fed by'the condenser, an electronic valve between the condenser and the coil to control flow therebetween, and timing means controlling the valve operation.

-6. In an ignition system, a direct current source of power, an induction coil, automatically operable means to produce a fluctuating current connected to the source, storage means connected to the automatically operable means and to the coil and a thermionic three-electrode valve connected between the storage .means and the coil to control the flow and a separately actuated timing de- 1 vice connected to the control electrode of the valve, its frequency of operation being entirely independent of the automatic fluctuating means.

DONALD W. RANDOLPH. 

